Of 195 cases of juvenile Huntington disease gathered from case descriptions, the sex, age at onset, duration of disease, clinical type, sex of the affected parent, as well as sex, mean age at onset and at death of adult cases in the same pedigrees were noted when available, and the data were investigated for evidence of relationships between different features. Examination of a subset of 112 cases showed a preponderance of rigid cases, whose affected parent proved to be the father in a significantly high number of cases. Rigid paternal cases had a significantly lower age at onset, as well as a shorter duration of disease than choreatic paternal cases. No such relationship exists between rigid maternal and choreatic maternal cases. In rigid cases duration of disease proved to be shorter for those with a lower age at onset. Female juvenile cases tended to have a lower age at onset than male ones, regardless of clinical type or sex of the affected parent. The mean ages at onset and at death of adult members of the same pedigrees were not related to clinical type or age at onset of juvenile cases. It is argued that juvenile Huntington disease should not be regarded as a separate clinical entity, but as a manifestation of the rigid variant of the disease.